This is the page that lists all of the peptide search results which BiblioSpec understands:
BiblioSpec always needs to find some sort of false discovery rate value, so the search results normally need to have been run through something like Percolator or Peptide Prophet.
Those .mzid files on that FTP server certainly mention "peptideprophet" in the <AnalysisSoftwareList> at the beginning of the file, but I don't see anything that looks like a Peptide Prophet score on the SpectrumIdentificationItem's.
I am not an expert on BiblioSpec peptide search result formats. If you wait until Monday someone who is more of an expert might be able to give you better information.
Hope this helps,